One of the more effective ways to reduce excessive drinking in college is also the most obvious — talk to freshman before they set foot on campus.

It turns out that discussing drinking in any way, including why some teens drink while others abstain, as well as the potential dangers of over-indulging, during the summer before students start school can both reduce the odds that light drinkers will escalate their alcohol intake, and increase the likelihood that already heavy-drinking teens will cut down or stop, according to new research.

Rob Turrisi of Penn State University and his colleagues surveyed 1,900 students and their parents just before the teens started college and again during the fall of their freshman and sophomore years. Their parents agreed to be randomized into one of four groups. One group used a handbook provided by the researchers to guide discussions, which occurred before freshman year, with their teens about drinking. The conversations were designed to be casual and nonjudgmental, with the parents providing accurate information about the reality of underage drinking and its risks, such as alcoholism and alcohol poisoning.

“The materials are designed for parents to pick and chose what they think is most important and what they think they can do best, given the individual relationship they have with their sons or daughters,” says Turrisi, “It respects the individuality and uniqueness of each relationship. That said, it will differ from family to family.” Some of the topics included why some teenagers drink while others abstain, alternative ways of getting the effects people seek from alcohol, as well as parents’ own drinking habits that served as models for responsible alcohol consumption.

Another group did the same thing, with some additional “booster” discussions later on. The third group didn’t start the discussion until after the students had already begun school and the fourth was a control group where parents were not instructed to take any particular action.

Before starting college, 51% of the students were nondrinkers, defined as not having had a drink in the past month, while 30% reported drinking heavily on some weekends and 15% drank moderately on weekends. Only 5% were frequent, heavy drinkers. But after 15 months of college — when most of the students would still not be of legal drinking age — only 25% were nondrinkers and 29% had become heavy drinkers.

Turisi and his team found, however, that the discussions about alcohol seemed to have some effect in curbing drinking habits, especially among students that started college as heavy drinkers. But timing was everything. If their parents talked to them about things like why people drink and substitutes for drinking before they left for school, they were 20 times more likely to transition to a more healthy drinking pattern—including nondrinking— than they were to stay heavy drinkers 15 months later.

In fact, the study found that the talks were only effective if they occurred before the students left for school — having a talk after college started was no more effective than doing nothing and adding “booster” conversations didn’t improve the results either. (A previous study of the same intervention suggested that additional discussions could help in reducing drinking and showed no evidence of harm.)

“By parents doing the intervention [before college], their young adult children are less likely to transition to high risk or heavy drinking groups while at college,” says Turrisi. “Young adult children who have already started high risk or heavy drinking are more likely to transition out of these groups while at college. In both cases, risk dramatically goes down,” he says.

Turrisi believes that the discussions can impact heavy drinkers because the conversations provide an opportunity for parents and their teens to better understand why the teens drink, and, if the alcohol is a coping mechanism for stresses or painful experiences, how they can find healthier ways of handling these pressures. “The heavy drinkers can explore the motivations they have for drinking,” he says.

The benefit of dialogue is that it provides an opportunity for understanding, and that connection alone can have a positive impact on reducing harmful behaviors such as underage drinking. Talk may be cheap, but it can also be pretty powerful.

The research was published in the Journal of Studies of Alcohol and Drugs.